Avalanche Forecast

Issued: Feb 21st, 2018 4:11PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada pgoddard, Avalanche Canada

Caution if the sun comes out - avoid steep sunny slopes where the snow will lose cohesion.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Mix of sun and cloud with flurries possible. Freezing level at valley floor. Light winds.FRIDAY: 2-5 cm snow. Freezing level near 500 m. Moderate to strong west to south-westerly winds. SATURDAY: Light snow. Freezing level near 300 m. Light winds.

Avalanche Summary

A widespread wind slab cycle was reported last weekend. Following the cycle, a few naturally and human-triggered size 1-2 avalanches have continued over the last few days. Most of these have been confined to recently built wind slabs, however a couple failed on deeper weak layers in the snowpack, especially when triggered from thin spots on a slope.It will still be possible to trigger a wind slab with the weight of a person in specific terrain. Persistent slabs could still be triggered from thin-to-thick snowpack areas, or with a heavy load. Be mindful of any steep slopes getting cooked by the sun and give these a healthy berth.

Snowpack Summary

You're likely to encounter highly variable snow surfaces after recent strong arctic outflow winds took out their fury on the upper snowpack. Fragile cornices and hard and soft wind slabs can be found on many alpine and treeline slopes. Ongoing cold temperatures are helping to break down and soften these. Windward slopes (roughly north to east facing) have been scoured back to an old crust. The wind slabs sit on various old surfaces including sun crusts, facets and spotty surface hoar (which is most prevalent in sheltered treed locations). Around 50-150 cm down, you'll find a crust/surface hoar layer from mid-January, which still has the chance to surprise you and could be triggered from a thin snowpack spot, or with a large trigger like cornice fall. Facets at the base of the snowpack can possibly be triggered from shallow snowpack areas.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs are lurking behind ridges and ribs on a variety of slopes.
Be cautious as you transition into wind affected terrain.Give cornices a wide berth when travelling on or below ridges.Travel on ridgetops to avoid wind slabs on slopes below.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Buried weak layers are most likely to be triggered from thin or variable depth snowpack areas; or with a large load like a cornice fall.
Avoid thin, rocky or sparsely-treed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3.5

Valid until: Feb 22nd, 2018 2:00PM

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